There is a need for additional ways of treating diseases associated with metabolic syndrome such as, for example, dyslipidemia, cardiovascular disease, obesity and diabetes (e.g., Type 2 diabetes).
Triglycerides or triacylglycerols are the major form of energy storage in eukaryotic organisms. In mammals, these compounds are primarily synthesized in three tissues: the small intestine, liver, and adipocytes. Triglycerides or triacylglycerols support the major functions of dietary fat absorption, packaging of newly synthesized fatty acids and storage in fat tissue (see Subauste and Burant, Current Drug Targets—Immune, Endocrine & Metabolic Disorders (2003) 3, pp. 263-270).
Diacylglycerol O-acyltransferase, also known as diglyceride acyltransferase or DGAT, is a key enzyme in triglyceride synthesis. DGAT catalyzes the final and rate-limiting step in the triacylglycerol synthesis from 1,2-diacylglycerol (DAG) and long chain fatty acyl CoA as substrates. Thus, DGAT plays an essential role in the metabolism of cellular diacylglycerol and is critically important for triglyceride production and energy storage homeostasis (see Mayorek et al, European Journal of Biochemistry (1989) 182, pp. 395-400).
Two forms of DGAT have been cloned and are designated DGAT1 and DGAT2 [see Cases et al, Proceedings of the National Academy of Science, USA (1998) 95, pp. 13018-13023, Lardizabal et al, Journal of Biological Chemistry (2001) 276, pp. 38862-38869 and Cases et al, Journal of Biological Chemistry (2001) 276, pp. 38870-38876]. Although both enzymes utilize the same substrates, there is no homology between DGAT1 and DGAT2. Both enzymes are widely expressed however some differences do exist in the relative abundance of expression in various tissues.
Disorders or imbalances in triglyceride metabolism, both absorption as well as de novo synthesis, have been implicated in the pathogenesis of a variety of disease risks. These include obesity, insulin resistance syndrome, Type II diabetes, dyslipidemia, metabolic syndrome (syndrome X) and coronary heart disease [see Kahn, Nature Genetics (2000) 25, pp. 6-7, Yanovski and Yanovski, New England Journal of Medicine (2002) 346, pp. 591-602, Lewis et al, Endocrine Reviews (2002) 23, pp. 201, Brazil, Nature Reviews Drug Discovery (2002) 1, pp. 408, Malloy and Kane, Advances in Internal Medicine (2001) 47, pp. 111, Subauste and Burant, Current Drug Targets—Immune, Endocrine & Metabolic Disorders (2003) 3, pp. 263-270 and Yu and Ginsberg, Annals of Medicine (2004) 36, pp. 252-261]. Compounds that can decrease the synthesis of triglycerides from diacylglycerol by inhibiting or lowering the activity of the DGAT enzyme would be of value as therapeutic agents for the treatment of diseases associated with abnormal metabolism of triglycerides.
Known inhibitors of DGAT include: dibenzoxazepinones (see Ramharack et al, EP1219716 and Burrows et al, 26th National Medicinal Chemistry Symposium (1998) poster C-22), substituted amino-pyrimidino-oxazines (see Fox et al, WO2004047755), chalcones such as xanthohumol (see Tabata et al, Phytochemistry (1997) 46, pp. 683-687 and Casaschi et al, Journal of Nutrition (2004) 134, pp. 1340-1346), substituted benzyl-phosphonates (see Kurogi et al, Journal of Medicinal Chemistry (1996) 39, pp. 1433-1437, Goto et al, Chemistry and Pharmaceutical Bulletin (1996) 44, pp. 547-551, Ikeda et al, Thirteenth International Symposium on Athersclerosis (2003), abstract 2P-0401, and Miyata et al, JP 2004067635), aryl alkyl acid derivatives (see Smith et al, WO2004100881 and US20040224997), furan and thiophene derivatives (see WO2004022551), pyrrolo[1,2b]pyridazine derivatives (see Fox et al, WO2005103907), and substituted sulfonamides (see Budd Haeberlein and Buckett, WO20050442500).
Also known to be inhibitors of DGAT are: 2-bromo-palmitic acid (see Colman et al, Biochimica et Biophysica Acta (1992) pp. 1125, 203-9), 2-bromo-octanoic acid (see Mayorek and Bar-Tana, Journal of Biological Chemistry (1985) 260, pp. 6528-6532), roselipins (see Noriko et al, (Journal of Antibiotics (1999) 52, pp. 815-826), amidepsin (see Tomoda et al, Journal of Antibiotics (1995) 48, pp. 42-7), isochromophilone, prenylflavonoids (see Chung et al, Planta Medica (2004) 70, v58-260), polyacetylenes (see Lee et al, Planta Medica (2004) 70, pp. 97-200), cochlioquinones (see Lee et al, Journal of Antibiotics (2003) 56, pp. 967-969), tanshinones (see Ko et al, Archives of Pharmaceutical Research (2002) 25, pp. 446-448), gemfibrozil (see Zhu et al, Atherosclerosis (2002) 164, pp. 221-228), and substituted quinolones (see Ko et al, Planta Medica (2002) 68, pp. 1131-1133). Also known to be modulators of DGAT activity are antisense oligonucleotides (see Monia and Graham, US20040185559).
Particular mention is made to PCT publication WO 2007/060140 (published May 31, 2007; applicant: F. Hoffmann-La Roche AG). Claim 1 therein discloses compounds of the formula:
wherein R1, R2, R3, R4, R5, R6 and R7 are described. Additional publications include WO 2008/141976 (published May 13, 2008); US 2009/0093497 (published May 1, 2009) and US 2009/0105273 (published May 1, 2009).
A need exists in the art, however, for additional DGAT inhibitors that have efficacy for the treatment of metabolic disorders such as, for example, obesity, Type II diabetes mellitus and metabolic syndrome.